Can MariTide Save Amgen Stock From Its Fading Blockbusters?

The biotech giant is bucking the market trend, but its real value for investors lies in a story that unfolds over years, not days.

In a week where the S&P 500 has stumbled, losing 2.6%, Amgen (AMGN) has been a bright spot, climbing 5.2%. That kind of divergence gets noticed. The company’s latest earnings call has investors focused on the potential of its obesity drug, MariTide, which management hopes can become a “new paradigm” with less frequent dosing than the current weekly options.

When a stock stands tall in a falling market, the instinct is powerful: chase the winner. It feels like a safe harbor, a sign of fundamental strength. But reacting to one week’s price action is a short-term game. The question that actually decides your long-term wealth is a different one. Does owning Amgen add a genuinely new source of returns to your portfolio, or does it just give you more of the same market risk you already hold in an index fund?

A Genuinely Different Engine For Your Portfolio

To answer that, we have to ignore the last five days and look at the last five years. Over that period, Amgen’s stock has a correlation of 0.32 to the S&P 500. In plain English, this means the vast majority of its performance has been driven by its own story, its drug pipeline, its sales, its specific business challenges, not by the daily tides of the broader market. Paired with an 11.5% annualized return over that time, this is the profile of an attractive, differentiated return stream. It adds something to a portfolio that an index fund doesn’t already provide.

This independence doesn’t mean it’s a sleepy stock. Amgen’s annualized volatility of 23.9% is higher than the S&P 500’s 17.1%. On days the market rises, it has tended to capture about 70% of the gain, and on down days, it has absorbed about 60% of the loss. It’s an asset with its own rhythm, but one that requires thoughtful sizing.

The Business Behind The Numbers: A High-Stakes Transition

The stock’s independent behavior makes sense when you look at the company’s situation. Amgen is navigating a major transition. The bull case is that its new growth drivers are more than ready to take the lead. On its latest earnings call, management highlighted that its six key growth drivers now represent “70% of our sales in the quarter and grew in aggregate by 24%.” This growth is powered by drugs like the cholesterol-lowering Repatha, which saw sales jump 34% year-over-year in the first quarter.

That momentum is critical because the bear case is just as clear: legacy blockbusters are fading. Combined sales for Prolia and XGEVA, two of its established drugs, fell 32% year-over-year in the same quarter. Management stated they “anticipate accelerated sales erosion over the remainder of 2026.” This dynamic puts substantial pressure on the pipeline, especially the high-profile MariTide program, to execute flawlessly and fill a significant revenue gap.

How To Think About Amgen Stock Now

Amgen’s multi-year behavior shows it can serve as a valuable partial diversifier in a portfolio. It’s not a perfect hedge designed to move opposite the market, but rather a return engine that runs on its own fuel. Its higher volatility means it’s a position to be sized with care, not one to pile into based on a few days of outperformance.

For investors, the single most important business signal to watch is the clinical progress of MariTide. The success or failure of this one drug program will likely be the dominant chapter in Amgen’s story for years to come, and it’s the real driver behind the stock’s differentiated path.

So, How Should You Hold A Stock Like Amgen?

Owning a strong performer is one thing; holding it in a way that fits the rest of your portfolio is another. The job is to size each position to the return it adds and the volatility it carries, so a single hot name never comes to dominate the risk you are taking. The Trefis High Quality (HQ) Portfolio is built on exactly that discipline, pairing the upside of strong businesses with the stability of a 30-stock portfolio, re-balanced with intent, and a track record of outperforming the S&P 500, S&P Mid-cap, and Russell 2000. Building a portfolio around how assets actually behave together, rather than which one ran hardest last week, is how you grow wealth while smoothing the ride.